Invoking private methods outside declaring class in AX 2012

Invoking private methods outside declaring class in AX 2012

Tutorial
Published on
Sep 17, 2015

There are three method accessibility modifiers in X++ language. It is well known knowledge of their purpose, as they are common for many programming languages.

Shortly, public allows for  unrestricted use by any classes, protected – only by derived and declaring, private narrows access to declaring class. So, by theory, we shouldn’t be able to access private method outside declaring class. In X++ this is true and false at the same time. How is it possible? Surprisingly, it is very simple. We only need to cast an instance of our class to the object type – base class from which all other classes are derived. Please apply and run following (pseudo) code and you will see.

class TestClass1

{

public void publicMethod()

{

   info("Hey, I'm public!");

}

protected void protectedMethod()

{

   info("Hey, I'm protected!");

}

private void privateMethod()

{

   info("Hey, I'm private!");

}

}

class TestClass2

{

public static void main(Args args)

{

   TestClass1 class1;

   Object objectClass1;

   class1 = new TestClass1();

   objectClass1 = class1;

   objectClass1.publicMethod();

   objectClass1.protectedMethod();

   objectClass1.privateMethod();

}

}

I personally see this functionality as a bug, but quite useful one. It happed to me already few times, that I had to invoke some private methods. Normally I would overwrite interested object and change its access modifier. But this approach is definitely not elegant. Firstly, having copy in upper layer can cause some problems when upgrading. Secondly, we globally and explicitly change developer’s will.

Summarizing, both solutions should be deeply considered before use, but one of them seems to be much easier to implement.

There is more. Similarly, we can also invoke private table methods. Of course instead of object type a common must be used.

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Written by
Marek Korejwo

Microsoft Dynamics programmer, consultant and enthusiast since 2009. Experienced in discrete production and media systems.